The present invention relates to a process for the preparation of acrolein, acrylic acid and mixtures thereof or methacrolein, methacrylic acid and mixtures thereof by the vapor phase reaction of allyl acetate or methallyl acetate and oxygen in the presence of a heterogeneous catalyst composition comprising a catalytically effective amount of palladium metal.
Acrolein and acrylic acid and methacrolein and methacrylic acid are very important chemicals and are particularly useful in the preparation of a variety of commercial products, including plastic sheet and molding powder for signs, emulsion polymers for water-based paint formulations, paper coating, and many other such applications.
A number of processes have been proposed for the preparation of these materials and are well-known in the art. See, for example, "Encyclopedia of Chemical Technology", Second Edition, Kirk-Othmer, Vol. 1, pages 293-295. Also, Chapter 10 of "Propylene and Its Industrial Derivatives", by E. G. Handcock, published by John Wiley, New York, 1973.
U.S. Pat. No. 3,792,086 describes a process employing a catalyst composition containing phosphoric acid and palladium metal in the preparation of acrylic or methacrylic acids by the vapor phase oxidation of propylene or isobutylene, respectively. A number of U.S. patents directed to the preparation of such products are noted therein. U.S. Pat. No. 3,758,551 discloses a vapor phase process for the preparation of acrylate and methacrylate esters. U.S. Pat. No. 3,947,495 shows an improved catalyst composition containing a sulfur modifier.
British Pat. No. 1,101,056 discloses a liquid phase oxidation process for the production of esters, aldehydes, ketones and acids by reacting a material such as allyl acetate in the presence of an aliphatic carboxylic acid with oxygen in a homogeneous redox system containing a palladium salt and a salt of copper or iron and further including chloride or bromide ions. Illustrative of the reaction solution is glacial acetic acid, palladium chloride, lithium chloride, lithium acetate, cupric acetate and allyl acetate. Serious disadvantages are associated with such homogeneous catalysis as, for example, difficulty encountered in separating the reaction product from the soluble catalyst. U.S. Pat. No. 3,625,996 shows a liquid phase process for preparing olefinic acids or esters from dicarboxylic acids or esters by contacting these compounds with a complex catalyst comprising a Group VIII noble metal and a ligand of organic phosphines, arsines or stibines.
Applicant's U.S. application Ser. No. 603,907, now U.S. Pat. No. 4,051,181, issued Sept. 27, 1977 shows a step-wise vapor phase process for the oxidation of propylene to acrylic acid via allyl alcohol.
It is among the objects of the present invention to provide a new and improved process for the preparation of acrolein, acrylic acid and mixtures thereof or methacrolein, methacrylic acid and mixtures thereof from allyl acetate or methallyl acetate by a direct and efficient vapor phase process.
Other objects and advantages of the invention will be apparent from the following description.